Adults between the ages of eighteen and twenty-five have the highest rate of cocaine use. Crack is powder cocaine that has been processed into a form that can be smoked. Crack and cocaine can cause heart attacks and brain hemorrhages and sometimes have fatal effects. During the 1980s the low cost of crack and its ability to produce an almost immediate high made it very popular. Although the use of both cocaine and crack has declined since then, these drugs remain a serious problem." United States. Smoking marijuana produces a general feeling of well-being but also impairs judgment, reaction times and decreases coordination According to the 2009 Youth Risk Behavioral Survey, 38 percent of ninth through twelfth grade students in public and private schools in the United States had used marijuana one or more times during their time in school..